It's a very simple job all you need is USB+Firmware (depending on the version)+USB Driver +ODIN (For original versions) that's all.

You install the USB Driver, but the phone is in downloader mode, enter your name and
show where the firmware is.

the firmware will start in 5-10 minutes.
As I said,

GT - S5830I Firmware 4.4.2 (version)

is written for this
example so that we can close the topic.

Note: Be careful not to turn off the light or disconnect the USB during
the firmware.

You can kill your smartphone.